Skywatch Line for Wednesday and Thursday, June 26 and 27, 2024, written by Alan French

This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, June 26 and 27, 2024, written by Alan French.

The Sun rises at 5:19 A.M. on Wednesday and sets at 8:38 P.M. On Thursday it also rises at 5:19 and sets at 8:38. In the northern hemisphere, we are past the summer solstice so we are now losing daylight. This Thursday has just 1 minute, 40 seconds less daylight than last Thursday. As we move ahead, the loss of daylight will gradually accelerate.

The Moon reached full last Friday and is now moving toward last quarter, which it will reach this coming Friday. The Moon does not rise until after midnight now. On Wednesday night the Moon will rise at 8 minutes after midnight on Thursday morning. Thursday night it will not rise
until 30 minutes after midnight Friday morning. The evening skies are now moonless and dark. Because of Daylight Saving Time, however, the night sky does not shed all vestiges of evening twilight until just before 11:00 P.M. In most places today, light pollution hides the last traces of evening twilight and darkness seems to fall earlier.

At 11 P.M. the constellation Hercules is high in the southern sky with parts of the sprawling star pattern stretching to the zenith. Hercules is the fifth largest constellation, and among those in the north, is the second largest. Look for a trapezium, or keystone, of stars, with the narrow end at the bottom. Below its narrow bottom is a wider pair of stars, and the six stars form a nice sideways butterfly. If you seek Hercules on a star chart, you will see stars extending outward from the extreme corners of the stellar butterfly.

Hercules is home to one of the celestial showpieces of the northern skies, the Great Globular Cluster, M13, a compact ball of stars. The “M” designation is from a list of 110 deep sky objects, nebulae, galaxies, and star clusters, mostly compiled by comet hunter Charles Messier and his friend and collaborator Piere Méchain, with a few later additions. For many beginning telescope users, observing all the Messier Objects is a rite of passage. The Astronomical League even offers a certificate for it.

M13 is easy to locate. It is between the right (west) two stars in the keystone of Hercules, about one-third of the way from the top star, Eta Herculis, to the bottom star, Zeta Herculis. Under truly dark skies, M13 is faintly visible by eye, but modest optical aid is usually required. It is easy to spot through binoculars or a telescope’s optical finder scope. Through a telescope, the big ball of stars is a lovely sight.

There is another nice globular cluster in Hercules, M92. Because of its more famous neighbor, it tends to get overlooked, but it is worth a visit. Its location is reasonably well marked, with the globular two-fifths of the way from Iota Herculis to Eta Herculis. It too is visible through binoculars or a telescope’s finder, but not as easy to spot as M13.

There is a third globular in Hercules, to the northwest of M92, NGC 6229. At magnitude +9.39, it is more of a challenge than M13, at magnitude +5.78, and M92, at magnitude +6.44. It also lacks good landmarks. It is a nice addition for more experienced observers.